Chapter III. Struggle for Existence
The term, Struggle for Existence, used in a large sense

I should premise that I use this term in a large and metaphorical sense,
including dependence of one being on another, and including (which is more
important) not only the life of the individual, but success in leaving
progeny. Two canine animals, in a time of dearth, may be truly said to
struggle with each other which shall get food and live. But a plant on the
edge of a desert is said to struggle for life against the drought, though
more properly it should be said to be dependent on the moisture. A plant
which annually produces a thousand seeds, of which only one of an average
comes to maturity, may be more truly said to struggle with the plants of
the same and other kinds which already clothe the ground. The mistletoe is
dependent on the apple and a few other trees, but can only in a far-fetched
sense be said to struggle with these trees, for, if too many of these
parasites grow on the same tree, it languishes and dies. But several
seedling mistletoes, growing close together on the same branch, may more
truly be said to struggle with each other. As the mistletoe is
disseminated by birds, its existence depends on them; and it may
metaphorically be said to struggle with other fruit-bearing plants, in
tempting the birds to devour and thus disseminate its seeds. In these
several senses, which pass into each other, I use for convenience sake the
general term of Struggle for Existence.